Add process-admin role to business-central user in OS images

All business-central images have the following user/roles declared for the business-central user: kie-server,rest-all,admin,kiemgmt

The problem with this is that this out-of-the-box user doesn't have "process-admin" role. This means that this user won't be able to see human tasks of other users. It's very important to fix this especially for kie-wb-monitoring console, the main purpose of which is jbpm runtime monitoring.